The present invention relates to Stirling cycle machines such as Stirling cycle cooling or power producing machines.
Conventionally, as in this kind of a Stirling cycle machine, a free-piston Stirling cycle machine is provided with a piston slidably inserted inside a cylinder and a driving device (this corresponds to an electromagnetic mechanism of the present invention) disposed at an outer peripheral side of a proximal end of said cylinder for reciprocally driving said piston is known (for example, in Japanese patent publication No. 3769751. Said driving device is comprising of: a mover connected to a proximal end of said piston, said mover comprising of a short cylindrical shaped supporter coaxially extended on an outer periphery at a proximal end side of said cylinder and a permanent magnet fixed to said supporter; and a stator comprising of an annular electromagnetic coil and an electromagnetic cores which are disposed in proximity to an outer periphery of said permanent magnet and a magnetic conducting portion (this corresponds to the inner yoke in the present invention) disposed in proximity to an inner periphery of said permanent magnet. Normally, as shown in FIG. 13, said magnetic conducting portion is arranged to have cylindrical shape as a whole by disposing sheet steels formed into predetermined shapes in a radial alignment, i.e. in an alignment which lateral direction of each sheet steel radiate from the central axis. Another type of a free-piston Stirling refrigerator is also known, which comprises of a holder provided with a movable yoke (this corresponds to the inner yoke in the present invention), said holder defining an electromagnetic driving mechanism for a free-piston Stirling refrigerator (this corresponds to the electromagnetic mechanism in the present invention), wherein a permanent magnet is attached to said movable yoke (for example, in Japanese un-examined patent publication No. 2004-180377). By attaching said permanent magnet to said movable yoke, there will be no gap between said inner yoke and said permanent magnet, and this results in preventing the magnetic flux density from decreasing and the power density of said electromagnetic driving mechanism can be enhanced.
[Reference 1]Registered Patent Publication No. 3,769,751[Reference 2]Unexamined Patent Publication No. 2004-180377